Synthesis of silica gel immobilized thiourea and its application to the on-line preconcentration and separation of silver, gold and palladium

摘要

A new silica gel based chelating sorbent with thiourea as a functional group was used for the flow injection (FI) on-line preconcentration and separation of trace levels of silver, gold and palladium. Its sorption characteristics were evaluated by FI-FAAS. The selected metal ions were adsorbed on a column packed with thiourea modified silica gel (TuSG) with a sampling flow rate of 5.0 ml min~(-1), eluted with 5% thiourea with a flow rate of 2.5 ml min~(-1) and determined by FAAS. Common co-existing ions did not interfere with the preconcentration and determination. The detection limits, defined as three times of the standard deviation of the bland (3#sigma#), of Ag, Au and Pd are 1.3, 14 and 21 ng ml~(-1), respectively, with a l min sample loading time. The RSD is not more than 3.0% for 0.040 #mu#g ml~(-1) of Ag, 0.20 #mu#g ml~(-1) of Au and 0.30 #mu#g ml~(-1) of Pd. With 40 min of the sample loading time, 1.0 ng ml~(-1) of Ag, 5.0 ng ml~(-1) of Au and 7.5 ng ml~(-1) of Pd were successfully preconcentrated. The total dynamic capacity of TuSG was 24.5, 50.9 and 30.3 mg g~(-1) for Ag, Au and Pd, respectively. The sorbent exhibited excellent stability. Its sorption properties did not change after 1000 cycles of use. The selected metals in a secondary nickel alloy, and anode slime, an electrolytic solution and three national certified ore samples were determined satisfactorily using the proposed method.